Optimism in early conceptual designs and its effect on cost and schedule growth: An update

This paper updates a previous effort investigating how the evolution of initial concept designs are related to the cost and schedule growth of missions. The paper shows examples of the design evolution, and associated cost and schedule growth, for twenty historical NASA missions. Issues behind the cost and schedule growth of missions are varied, but in part may be attributed to systems that have changed substantially from those examined at initial concept through to launch. Historical resource growth is investigated for a variety of missions and mission types to provide guidelines and lessons learned to be used during the initial conceptual design stage for future missions. The data developed for the paper should help both project managers and cost and schedule estimators to develop more robust estimates earlier in the design process.